Injector

Abstract

An enclosure member includes a throughhole that penetrates a cover portion. The cover portion includes a blocking portion that receives an abutment by a wall portion to close an opening of an outflow passage with respect to spaces outside of the enclosure member. The blocking portion is provided so as to surround an opening of the throughhole, and the throughhole is in communication with the outflow passage even when the blocking portion is abutting the wall portion. Further, a spring is outside of a back pressure chamber to bias the enclosure member. The enclosure member itself blocks outside spaces from the back pressure chamber, so the expenditure of high pressure fuel may be controlled, and an injection hole may be opened and closed by a needle.

The invention claimed is: 
     
       1. An injector, comprising:
 a needle which is a valve body configured to open and close an injection hole that injects fuel; 
 a body which has a cylindrical shape and which houses the needle therein, the body having the injection hole; 
 a back pressure chamber for exerting a back pressure of fuel on the needle in a direction of closing the injection hole; 
 an outflow passage that allows fuel to flow out of the back pressure chamber; 
 a drive unit configured to open and close the outflow passage based on a control signal from a controller, thereby increasing or decreasing the back pressure to operate the opening and closing of the injection hole via the needle; 
 an enclosure member that includes
 a cover portion configured to cover a rear end of the needle from a rear side, and 
 a cylinder portion configured to be in slidable contact with an outer circumferential surface of the needle to slidably support the needle, the rear end of the needle being surrounded by the cover portion and the cylinder portion to form the back pressure chamber on a rear end side of the needle; 
 
 a spring configured to bias the enclosure member toward the rear side; and 
 a wall portion disposed on the rear side of the cover portion and configured to receive an abutment of the cover portion to regulate movement of the enclosure member toward the rear side, the wall portion including an opening of the outflow passage, wherein 
 the enclosure member includes at least one throughhole that penetrates through the cover portion, 
 the cover portion includes a blocking portion that, when the cover portion abuts the wall portion, blocks the opening of the outflow passage with respect to spaces outside of the enclosure member, 
 the blocking portion is provided so as to surround an opening of the throughhole, the throughhole being in communication with the outflow passage even when abutting the cover portion, and 
 the spring is outside of the back pressure chamber to bias the enclosure member. 
 
     
     
       2. An injector, comprising:
 a needle which is a valve body configured to open and close an injection hole that injects fuel; 
 a body which has a cylindrical shape and which houses the needle therein, the body having the injection hole; 
 a back pressure chamber for exerting a back pressure of fuel on the needle in a direction of closing the injection hole; 
 an outflow passage that allows fuel to flow out of the back pressure chamber; 
 a drive unit configured to increase or decrease the back pressure based on a control signal from a controller to operate the opening and closing of the injection hole via the needle, the drive unit including a three way valve that switches the outflow passage between two connections, the outflow passage being connected to one connection when the back pressure is to be decreased, the outflow passage being connect to another connection when the back pressure is to be increased; 
 an enclosure member that includes
 a cover portion configured to cover a rear end of the needle from a rear side, and 
 a cylinder portion configured to be in slidable contact with an outer circumferential surface of the needle to slidably support the needle, the rear end of the needle being surrounded by the cover portion and the cylinder portion to form the back pressure chamber on a rear end side of the needle; 
 
 a spring configured to bias the enclosure member toward the rear side; and 
 a wall portion disposed on the rear side of the cover portion and configured to receive an abutment of the cover portion to regulate movement of the enclosure member toward the rear side, the wall portion including an opening of the outflow passage, wherein 
 the enclosure member includes at least one throughhole that penetrates through the cover portion, 
 the cover portion includes a blocking portion that, when the cover portion abuts the wall portion, blocks the opening of the outflow passage with respect to spaces outside of the enclosure member, 
 the blocking portion is provided so as to surround an opening of the throughhole, the throughhole being in communication with the outflow passage even when abutting the cover portion, and 
 the spring is outside of the back pressure chamber to bias the enclosure member. 
 
     
     
       3. The injector of  claim 1 , wherein
 the spring is set so as to bias the enclosure member toward the rear side and also to bias the needle toward a leading side, and 
 the needle is moved toward the leading side by the biasing force of the spring and the back pressure. 
 
     
     
       4. The injector of  claim 1 , wherein
 an abrasion resistance treatment is performed on the blocking portion and the wall portion. 
 
     
     
       5. The injector of  claim 2 , wherein
 the spring is set so as to bias the enclosure member toward the rear side and also to bias the needle toward a leading side, and 
 the needle is moved toward the leading side by the biasing force of the spring and the back pressure. 
 
     
     
       6. The injector of  claim 2 , wherein
 an abrasion resistance treatment is performed on the blocking portion and the wall portion.